The use of N,N'-substituted piperazine is disclosed in a number of documents. U.S. Pat. No. 5,192,766 purports to disclose N-acryloylpiperazine derivatives and their pharmaceutical use as platelet activating factor antagonists. While the title uses the term N-acryloylpiperazine, it is clear from the disclosure that the compounds disclosed have a phenyl substituent bonded to the alpha,beta-unsaturated acylamido group such that the compounds are, thus, apparently cinnamoyl derivatives or homologues thereof.
M. Taningher et al., "Genotoxicity of N-acryloyl-N'-phenylpiperazine, a Redox Activator for Acrylic Resin Polymerization", Mutation Research, vol. 282, pp. 99-105 (1992) discusses the use of N-acryloyl-N'-phenylpiperazine as a promoter of redox reactions in place of other tertiary aromatic amines, e.g. N,N-dimethylaniline. It is speculated that the acryloyl group will allow the compound to be copolymerized into the final material and thus avoid release thereof into the environment.
U.S. Pat. No. 5,045,427 discloses the use of a variety of polymerizable compounds, including N,N'-bis-acrylamido-piperazine, in a photographic material. This photographic material is comprised of a support on which is provided a light-sensitive layer comprised of a photosensitive silver halide, a non-photo-sensitive silver salt, a reducing agent, a color image-forming material and a polymerizable compound.
EP-0356960 discloses polyacrylamide gels which employ as crosslinking agents diacylyl compounds with tertiary amide groups, e.g. diacrylyl piperazine (a.k.a. N,N'-bis-acrylamido-piperazine). These gels contain a chaotropic agent which permits the use of the gels in the separation of proteins or nucleic acids.
U.S. Pat. No. 3,510,247 discloses the modification of cellulosic materials with tertiary bis-acrylamides, e.g. diacryloyl piperazine (a.k.a. N,N'-bis-acrylamido-piperazine). The bis-acrylamide is applied to the cellulosic substrate and a crosslinking reaction is catalyzed by the use of an alkaline compound and elevated temperatures, generally 200 degrees F. to 350 degrees F. U.S. Pat. No. 3,528,964 discloses a similar modification, but the amides are sulfonic acid amides, wherein the sulfonic acid groups contain ethylenic unsaturation.
The technology for the production of coatings by curing monomeric compositions on the surface of various substrates is generally known. For example, J. Lowell, "Coatings", Encyclopedia of Polymer Science and Engineering, vol. 3, pp. 615-675, discusses, at page 647, the production of coatings by free-radical polymerization of monomers, e.g unsaturated polyesters in a solution of an unsaturated monomer such as styrene, acrylates, and methacrylates, and polyfunctional low volatility monomers such as trimethylolpropane triacrylate. When such systems are cured with ultra-violet radiation, a photoinitiator such as benzophenone is often used to increase the production of free-radicals and thereby promote curing of the coating.
While N,N'-bis-acrylamido-piperazine is a useful monomer in many applications, it has been found its performance as the major component of a radiation curable composition has certain drawbacks. For example, it has been observed that cured films thereof are quite brittle.